Of 229 necropsy patients with diabetes mellitus (DM) with onset after age 30 years, 164 had clinical evidence of coronary heart disease (CHD) and 65 did not. The observations in the 229 diabetic patients were compared to those in 183 age-sex-matched non-diabetic patients with CHD. The average number of 3 major (right, left anterior descending, left circumflex) coronary arteries per patient narrowed greater than 75% in cross-sectional area by atherosclerotic plaque was similar in the DM patients with or without clinical CHD and both groups were similar to the non-DM patients with CHD: (DM - CHD vs. DM plus CHD vs. CHD - DM: 2.4/3.0: 2.6/3.0: 2.5/3.0).